Influence of thermal annealing on the structural and optical properties of polycrystalline Cd0.96Zn0.04Te thin films

Abstract

The influence of thermal annealing on the structural and optical properties of Cd0.96Zn0.04Te thin films were studied by XRD, AFM, optical transmittance measurement and Raman scattering. The polycrystalline Cd0.96Zn0.04Te films were deposited onto well-cleaned glass substrates (Corning 7059) maintained at room temperature and are anneled. The films were stoichiometric as analyzed by RBS and EDAX. The films exhibited zinc blende structure with predominant < 111 > orientation. The intensity of the < 111 > peak increases and the FWHM decreases on thermal annealing. The rms roughness of the as-deposited film is 3.7 nm and the value decreases on annealing. The direct allowed band gap value of the room temperature deposited films is 1.523 eV which decreases on thermal annealing. The Raman spectra of the films show longitudinal- and transverse-optical (LO, TO) modes, which arise from CdTe- and ZnTe-like vibrations. The intensity of the peaks increases and the FWHM decreases with the increase in annealing temperature indicates the improvement of crystallinity on thermal annealing.